Footwear sole structure

ABSTRACT

A dynamic footwear midsole has an upper layer and a lower layer that are connected by a group of heel slats and a group of forepart slats, each slat being connected at hinge regions to the upper and lower layers. The slats in each group are arranged in generally paralleling planes with the heel slats and forepart slats being arranged to cause one group to collapse as the other group expands. An arch support is provided at the midportion of the upper layer is constructed to enable the upper layer to rock about the arch support.

FIELD

The present invention relates to sole structures for footwear and,particularly to footwear having an improved midsole structure.

BACKGROUND

Many types of footwear typically are formed on a last, a foot-shapedform. In a common construction an insole is temporarily attached to thebottom of the last and an upper is draped and stretched over and aboutthe last and the margins of the upper are attached to the peripheralmargins of the insole. An outsole then is attached to the shoe bottom.In many types of footwear, for example only, in athletic shoes, amidsole may be provided between the insole and outsole. The midsole mayfunction to provide stability and cushioning for the user's foot, toenhance comfort, reduce risk of injury or to serve other functions.Midsoles commonly are formed from resilient polymeric materials and mayhave varying degrees of compressibility, resilience and othercharacteristics depending on the combinations of materials used, midsoleshape and geometry.

It is among the general object of the present invention to provide animproved midsole construction and improved footwear embodying animproved midsole structure.

SUMMARY

A midsole is provided to have an upper layer and a lower layer spacedbelow the upper layer, each layer having a peripheral contourapproximating a human footprint. The upper layer, which is relativelystiff longitudinally, has an arch support formed in its mid-region. Theupper and lower layers are connected by a plurality of slats that extendtransversely of the midsole. The slats are arranged in two groups,including a forepart group located between the arch support and the toeregion and a heelward group located between the arch and heel end of themidsole. The slats in the forepart group are inclined in an upward andtoeward attitude, and are in generally paralleling planes and the slatsin the heelward group are inclined in an upward and heelward attitude,and also are in a generally paralleling planes. The junctions of theslats with the upper and lower layers are formed to define hinge regionsthat enable the upper layer to move relative to the lower layer as theuser walks or runs. The region beneath the arch support is reinforced tobe more resistant to heightwise compression so that it can function in afulcrum-like fashion to support the foot as it pivots to transfer weightfrom heel to toe in a walking or running gait.

THE DRAWINGS

The objects and advantages of the invention will be apparent more fullyfrom the following description, with reference to the accompanyingdrawings in which:

FIG. 1 is a somewhat diagrammatic side view of a shoe having a midsolein accordance with an embodiment of the invention;

FIG. 2 is a plan view of the midsole as seen from 2-2 of FIG. 3;

FIG. 3 is a side view of the midsole;

FIGS. 4A and 4B are views of heel slats as seen along the lines 4A-4Aand 4B-4B of FIG. 2;

FIGS. 4C and 4D are views of forepart slats as seen along the lines4C-4C and 4D-4D of FIG. 2;

FIG. 5 is a somewhat diagrammatic, longitudinal section of the midsolewhen a runner's weight is on the heel, as shown in FIG. 5A:

FIG. 5A illustrates a runner with weight on the heel of the midsole;

FIG. 6 is a somewhat diagrammatic, longitudinal section of the midsolewhen a runner's weight is on the arch as shown in FIG. 6A:

FIG. 6A illustrates a runner with weight on the arch of the midsole;

FIG. 7 is a somewhat diagrammatic, longitudinal section of the midsolewhen a runner's weight is on the forepart, as shown in FIG. 7A; and

FIG. 7A illustrates a runner with weight on the forepart of the midsole;

FIGS. 8A and 8B are illustrations similar to FIGS. 4A and 4B of heelslats in a modified embodiment; and

FIGS. 8C and 8D are illustrations similar to FIGS. 4A and 4B of forepartof the invention, slats in a modified embodiment; and

FIG. 9 is an diagrammatic illustration of a user's foot with the user'sweight on the forepart of the midsole in the region of a modifiedforepart slat.

ILLUSTRATIVE EMBODIMENTS

As shown in FIG. 1, an illustrative article of footwear, such as anathletic shoe, has an upper 10, an insole (not shown), a midsole 12 andan outsole 14. The midsole 12, also shown in FIGS. 2-5, has an upperlayer 16 and a spaced lower layer 18, both of which have a peripheraledge 20 in a general outline of a human footprint.

The midsole may be formed from any of a variety of commerciallyavailable polymers, as by injection molding or by using additivemanufacturing techniques (e.g., 3-D printing) and may be considered tohave a heel portion 22, a forepart portion 24 and a midportion 26between the heel and forepart portions 22, 24. The upper and lowerlayers 16, 18 are connected together by a plurality of inclined slats,including a group of forepart slats 28 and a group of heel slats 30. Theupper layer 16 is provided, in its midportion 26, with an arch support32. As described in more detail below, the arrangements of heel slatsand forepart slats allow the heel and forepart regions of the midsole tobe resiliently compressed, alternately, while also permitting somerelative longitudinal movement of the layers in response to the shiftingweight of the user when walking or running. In the embodiment shown inFIGS. 2 and 3 the slats 28, 30 may extend transversely the full width ofthe midsole from the inner (medial) side M to the outer (lateral) side Lor may be modified as described below. As shown in FIG. 2, the slats 28,30 may be oriented at an angle A to the midsole centerline 31 (extendingbetween the heel and toe extremities of the midsole), preferably betweenabout ten to about twenty degrees with the medial ends of the slatsbeing disposed toeward of their lateral ends as I have found this toprovide a more comfortable configuration. The principles of theinvention, however, are not limited to any specific angle, and in somecases the slats could extend closer to perpendicular to the centerline.

The slats within each group are disposed in generally paralleling planesand are attached to and extend between the upper and lower layers 16, 18at upper and lower hinge regions 34, 36, respectively. The hinge regionsand materials from which the midsole is formed should provide for acumulative, desired degree of resilience to provide cushioning as weightis applied as well as contributing to forward propulsion as the weightis transferred from heel to toe. It will be appreciated that thearrangement of any pair of adjacent slats and the segments (16 a, 16 b,. . . 16 n and 18 a, 18 b, . . . 18 n) of the upper and lower layersthat connect to that slat pair define and function as a four-bar linkagethat encloses a variable, prism-shaped cell or void 38.

Although the slats in each group are generally parallel to each other,the slats 30 of the heel group are not parallel to the slats 28 of theforepart group. Thus, as shown, the forepart slats 28 are inclined in anupward and toeward orientation; the heel slats 30 are inclined in anupward and heelward orientation. This orientation of the slats 28, 30,coupled with the compressive resistance of the arch support region ofthe midsole, provides a dynamic action in which, the upper layer 16 canrotate about the arch support 32, which functions as a fulcrum, as theuser's weight shifts progressively from heel to toe. Thus, as shown inFIGS. 5 and 5A, as a runner's heel engages the ground, the heel regionof the midsole is compressed against the resilience of the heel region,causing the heel slats 30 to rotate within the midsole (counterclockwiseas seen in FIG. 5). That, in turn, causes the forepart portion 24 of therelatively stiff upper layer 16 to pivot relative to the lower layer andabout the arch support, causing the forepart of the upper layer to moveaway from the lower layer 18 with the forepart slats 28 rotating (alsocounterclockwise) as the spacing between the forepart portions of theupper and lower layers increases. As the runner's weight unloads fromthe heel portion 22 and shifts to the midportion 26 (FIGS. 6 and 6A) andthen to the forepart portion 28 (FIGS. 7 and 7A) of the midsole, theheel slats 30 and forepart slats 28 rotate within the midsole(clockwise), the stored restorative resilient force of the heel portionmay aid the runner as weight is transferred forwardly to cause resilientcompression of the forepart region. As the runner's stride continues andthe forepart is unloaded, the stored restorative resilient force of theforepart portion resilience may aid in the runner's forward motion.

The arch support is contoured to support the arch region of the user'sfoot and, preferably, may be formed integrally as a unit with the upperlayer. The upper layer should be relatively stiff along the length ofthe midsole, sufficiently so that the slats and their connectingsegments of the upper and lower layers function as a four-bar linkagesas described above, without significant distortion of the slats andconnective segments (16 a, 16 b . . . 16 n and 18 a, 18 b, . . . 18 n)of the layers. The stiffness can be achieved by various combinations ofmaterial selection, dimensional adjustments, and embedded stiffeners, aswill be familiar to those skilled in the art. The arch support should bethe least compressible portion of the midsole to facilitate its functionas a fulcrum. To that end the arch support may extend from the junctionregion of the most toeward slat 30 h of the heel group to the mostheelward forepart slat 28 f, both of which may be thicker and have morerobust hinge regions to provide support for the arch. Additionalsupports may be included as supplemental support below the arch as, forexample, by one or more heightwise and longitudinally extending supportbraces extending between the underside of the arch and the lower layer,the forward and rearward ends of the brace(s) being attached to thesupport slats 30 h and 28 f.

FIGS. 8, 8A, 8B, 8C and 8D illustrate modified embodiments of slats inwhich the one or both of the end regions of the slats may be modified byeliminating some end portions of some of the slats. In thismodifications, selected ends of selected slats may have cut-awayportions CA that have the effect of varying the degree of medial-lateralsupport provided by the midsole. For example, FIG. 8D illustrates anexample of a slat configuration with a greater cut-away on the medialend M of the slat than on the lateral end L so that the user's foot willtend to cant as shown in FIG. 9. It will be appreciated that theconfigurations of the slats, as well as other parts of the midsole maybe modified to provide a midsole having support characteristics tailoredand customized to a particular user, for example, to provide enhancedperformance, greater comfort, an appropriate corrective function orother characteristic. Commercially available gait analysis systems maybe employed to analyze a user's gait so as to inform making of suchcustomized midsoles.

Midsoles in accordance with the invention are not limited to use inathletic footwear but may be used with other types of footwear such asconventional shoes, sandals, hiking and other boots, flip-flops, amongothers. It should be understood that the foregoing description of theinvention is intended merely to be illustrative thereof and that otherembodiments and modifications may be apparent to those skilled in theart without departing from the principles of the invention.

1. A footwear midsole comprising: an upper layer; a lower layer; each ofthe layers having a heel portion, a midportion and a forepart portion;an arch support at the midportion of the upper layer; a plurality ofgenerally planar heel slats extending transversely between and hingedlyconnected to the heel portions of the upper and lower layers; aplurality of generally planar forepart slats extending transverselybetween and hingedly connected to the forepart portions of the upper andlower layers; the arch support being of sufficient strength to presentgreater resistance to heightwise compression than the heel and forepartregions;
 2. The midsole as defined in claim 1 further comprising: theheel slats being inclined in an upward and heelward direction; and theforepart slats being inclined in an upward and toeward direction.
 3. Themidsole as defined in claim 1 further comprising: the upper and lowerlayers and the slats being formed as a unitary, one-piece structure. 4.The midsole as defined in claim 2 further comprising: the upper andlower layers and the slats being formed as a unitary, one-piecestructure.
 5. The midsole as defined in claim 2 further comprising: thearch support extending between the most toeward slat of the heelwardgroup and the most heelward slat of the forepart group
 6. The midsole asdefined in claim 5 further comprising: the most toeward slat of the heelgroup and the most heelward slat of the forepart group being attached,respectively, to the upper layer at the toeward and heelward regions ofthe arch support.
 7. The midsole as defined in claim 6 furthercomprising: the most toeward slat of the heel group and the mostheelward slat of the forepart group being thicker and having lessflexible hinge regions than the other slats.
 8. The midsole as definedin claim 6 wherein the support structure for the arch support furthercomprises: at least one longitudinally and heightwise extending supportbrace connected between the upper layer and the lower layer and betweenthe most heelward slat of the forepart group and the most toeward slatof the heel group.
 9. The midsole as defined in claim 1 and having acenterline extending between the heel and toe extremities and furthercomprising: the slats extending at a non-perpendicular angle to thecenterline with the medial ends of the slats being toeward of the theirlateral ends.
 10. The midsole as defined in claim 9 wherein the angle isbetween about ten and twenty degrees.
 11. The midsole as defined inclaim 2 wherein the slats in each group are arranged in generallyparalleling planes.
 12. The midsole as defined in claim 1 wherein theupper and lower layers and longitudinally spaced slats define aplurality of hollow prism-shaped cells, each being defined by a pair ofadjacent slats and a segment of each of the upper and lower layers. 13.The midsole as defined in claim 2 wherein the upper layer issufficiently stiff to enable the upper layer to rock about the region ofthe arch support in heelward and toeward directions.
 14. The midsole asdefined in claim 12 wherein the upper layer is sufficiently stiff toprevent distortion of the segments of the upper layer in response torocking of the upper layer about the arch region.
 15. An article offootwear comprising: an upper; a midsole as defined in claim 1 attachedto the upper; and an outsole attached to the lower layer of the midsole.